Children are involuntarily exposed to tobacco both in utero through maternal smoking and during childhood from secondhand smoke (SHS). SHS exposure is associated with important health problems such as low birth- weight, asthma induction, asthma exacerbation, increased ear and lower respiratory infections, and sudden infant death syndrome. Notably, SHS exposure and the health effects of SHS vary by race, ethnicity and SES. Therefore, efforts to eliminate childhood exposure to SHS are critical for the reduction of health disparities. Because children have limited options for avoiding exposure, effective public health measures are needed to identify children at risk, increase parental smoking cessation, and implement home smoking restrictions, particularly with respect to minority households. An accurate, noninvasive method to objectively measure SHS would increase the nation's capacity to assess tobacco exposure risk in small children and minorities, who are often under-represented in research. Dried blood spots have been called a "gold mine" for assessing toxic exposures. They are obtained easily, and thousands of samples can be available to assess exposure levels across a population. Analysis of tobacco constituents in dried blood spots would afford an opportunity to objectively measure tobacco exposure on a population level. The goal of this project is to study disparities in childhood exposure to SHS by measuring cotinine, a biomarker of tobacco exposure. We propose to (1) develop high throughput liquid chromatography tandem mass spectrometry (LC/MS/MS) methods to quantify cotinine in dried blood spots;(2) estimate the U.S. population prevalence of in utero tobacco toxicant exposure by race by applying high throughput cotinine assay methods to extant dried blood spots collected during routine neonatal screening (n~2900);and (3) estimate the rate of SHS exposure in children ages 6-36 months by race by applying high throughput cotinine assay methods to extant dried blood spots collected to screen for lead exposure (n~3400). This application employs a multidisciplinary team with expertise in tobacco research (including the analytical methods to quantify nicotine metabolites), pediatric epidemiology, and health disparities research. The proposal is well-suited to the two-year "GO" grant mechanism because of the ability to rapidly access the important resource of extant dried blood spots from neonates and children that will yield thousands of individual samples. High throughput methods to measure cotinine in dried blood spots will provide opportunities to do all of the following: increase the reach of risk assessment into diverse communities, accurately measure SHS exposure, increase identification of childhood SHS exposure, move biomarker measurement of SHS exposure into the clinical arena, address tobacco-related health disparities, and inform changes in health care policy. The methods developed will provide an important resource to future epidemiological and clinical research initiatives that have potential to improve the health of children by reducing SHS exposure -- an important threat to public health. PUBLIC HEALTH RELEVANCE: This project will contribute to reducing disparities in health effects from tobacco among children. We will accomplish this goal by creating a powerful tool to objectively measure secondhand smoke exposure that is especially suited to use in young and minority populations and test the method in a large sample of dried blood spots from a diverse population of infants and children.